Technical Field
The present invention relates to a rotating electric machine mounted in a vehicle or the like and used as an electrical motor or a generator.
Related Art
A known rotating electric machine mounted in a vehicle, such as a vehicle alternator disclosed in Japanese Patent Application Laid-Open Publication No. 1999-164499, includes a stator and a rotor. The rotor includes a field coil and a Lundell core formed of a cylindrical portion, a yoke portion on an outer circumference of the cylindrical portion and a claw-shaped magnetic pole portion shaped so as to surround the field coil.
Another known rotating electric machine is a rotating field type synchronous motor as disclosed in Japanese Patent Application Laid-Open Publication No. 2006-254599 having permanent magnets imbedded in a rotor (referred to as an interior permanent magnet (IPM) motor).
The above rotating electric machines may utilize, as a coil wire, a rectangular wire having a rectangular cross-section matched in shape to slots of a stator core to increase a space factor of a stator coil wound in the slots of the stator core. Since such a rectangular wire commonly has a large cross-sectional area, eddy current generated in the coil wire may become problematic.
In some of motors including the Lundell core as disclosed in Japanese Patent Application Laid-Open Publication No. 1999-164499, the Lundell core is greater in axial length than the stator core. Also in some of IPM motors, the rotor core is greater in axial length than the stator core to increase the amount of flux. The rotor cores of these motors are prone to flux leakage flowing from the rotor core into coil ends of the stator coil exposed from the stator core. The coil ends are susceptible to large magnetic flux variations, which may cause large eddy-current losses, which may in turn cause heat generation.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing a rotating electric machine capable of reducing flux leakage flowing from a rotor core toward coil ends of a stator coil, thereby reducing eddy-current losses in the coil ends.